The notion of a transaction is an important concept for transactional systems, such as database management systems, recoverable file systems and transaction-based operation systems. Briefly stated, a transaction is an action or set of actions that guarantees the ACID (Atomicity, Consistency, Isolation and Durability) properties. Transactional logging involves maintaining a transactional log that durably records a time serial history of transactions in a system. A transactional log provides information for restoring a system to a particular state in time prior to a system failure. ARIES (Algorithm for Recovery and Isolation Exploiting Semantics) is one very popular recovery scheme used for restoring a failed system through transactional logging. To be ARIES compliant, a transactional logging system must meet certain conditions that enable the ARIES recovery scheme to function. For example, ARIES requires that log sequence numbers (identifiers that are used to specify a location of each record in a physical log) be strictly increasing.
Traditionally, ARIES compliant logging systems have used a dedicated log to support a single log client. ARIES compliance is desirable because the resulting logging system is typically very robust and achieves a high performance level. However, the inventors have determined that the high level of reliability of a single log client using a dedicated logging system may actually result in overall performance degradation for a computing environment where multiple log clients are using multiple dedicated logging systems. One of the reasons for this is that each dedicated logging system independently incurs input/output (I/O) overhead to write and retrieve information. The I/O overhead results in adverse performance impact, and the impact is cumulative for each of the independent logging systems. An improved logging system is desirable that could overcome some of these performance problems. However, the development of an improvement to the existing scheme of transactional logging has met several hurdles. The inventors have determined that one hurdle to an improved transactional logging system is the need to uniquely identify each log client with log records that may be stored on permanent storage in a manner consistent with the ARIES recovery scheme.